A variety of commercially available coordinate measurement machines have been used for measurement of parts of various type including airfoils. Such machines take readings of surface points by moving mechanical or optical probes along the surface of the part in a continuous motion or by moving the probes to discrete points along the surface to digitize the surface and thus provide a data file which can be analyzed to obtain dimensions of the part. In high production operations where every production part must be quickly and accurately measured and the apparatus is in nearly constant use, a very robust system is required to stand up under the load. In the case of air foils, a single turbine blade may require the measurement of say, 840 distinct points on 28 different sections to an accuracy of a few ten-thousandths of an inch and the complete survey of the blade should be completed within 40 minutes. In so doing the measurement, the probe (assuming a mechanical contact type) must efficiently move from point to point, gently touching the surface in each site and yet moving quickly between points and not colliding with the blade or the fixture holding the blade. The number of measurement points must not be compromised lest the measurement accuracy suffer.
U.S. Pat. No. 4,755,952 to Johns discloses a turbine blade measurement method and apparatus which uses a probe which is continuously scanned across the surface to track chordal sections of the part and a program analyzes the data for conformation to a desired part envelope.
U.S. Pat. No. 4,724,525 to Purcell et al is directed to a multi-axis measuring machine which moves an analog probe continuously across a surface and takes readings at specific points for use in subsequent data analysis. Three options are given for determining data points: time elapsed, distance traveled, and operator command.
U.S. Pat. No. 4,653,011 to Iwano disclose a coordinate measuring instrument for moving a probe in a stored path along a surface to be measured and takes readings at discrete points. Measurements are based on the readings.
U.S. Pat. No. 4,679,331 to Koontz discloses a method of measuring the contour of bent glass by moving a probe around a path of a fixture and making measurements at many points to teach a path to the control. After glass is inserted in the fixture the same path is automatically followed to measure the glass and determine its contour relative to the fixture.
U.S. Pat. No. 4,370,721 to Berenberg et al discloses an NC machine tool programmed to measure features on a rough part prior to machining to determine any offsets which may be used to modify the machining program. No adjustments of the measuring program are made.